Water resources at Tinos Ecolodge

The initial design concept of ELT, when it was founded in 2014, was to utilize every available
water resource in order to minimize the demand of high quality fresh water from the water
network. On the conventional side there is the connection to the public water grid that provides all
usages for high quality drinking water such as sinks and showers. On the non conventional side
there is rainwater, river water and treated sewage water. At the ELT we use all four sources of
water, however most of the water needs are covered by non conventional sources. The rainwater is
captured through a broadly designed harvesting system, which is connected to all hard surfaces
like roofs, stairs and verandas throughout the housing area. The old Cistern with a storage capacity
of a 100m3, functions as the central storage from where the water is distributed by pumping
throughout the rainwater network. This utility water network provides all points with water where
the quality can be below drinking water standards. This includes irrigation water, outside tabs for
cleaning, general purposes and also serves the toilette flush system. The sewage water which is
transported through a split grey-black water canalization is treated by a CW-vf unit, where the
effluent is collected in a cistern for utilization as irrigation water for ornamental non edible plants
or can be injected into the toilet flushing network if rainwater reserves run low. The river water is
used to supplement the irrigation water for the agricultural production. The table below shows an
overview of the different water qualities and the according utilization. In an off-the-grid situation
as applying to ELT it is important to be able to react fast to upcoming malfunctions of different sub
systems till the error is solved. This is described in the emergency row where in case of error or
shortage different bypasses can be made in order to keep the overall system running. These
bypasses become crucial in the case of a malfunction e.g. concerning the vegetable production
where 2-3 days without water can lead to a total production loss.

Current water loops at Tinos Ecolodge

The water loop already implemented before the HYDROUSA project is the usage of the treated sewage water
for toilet flushing. This can be described as a full loop where a certain amount of consumed fresh
water is returned to the consumer multiple times (figure 1.6). Due to the evapotranspiration
losses in the CW-vf treatment unit and the piping losses the loop depends on a constant
supplement of fresh water. Through out the time the system is running our experience show a
total loss of around 15-50% depending on the weather conditions throughout the year.

ELT tries to market ecological responsible tourism, this includes an information talk with every new
arriving customer about the water scarcity and how everybody can contribute positively, through
conscious behavior. But in the end it is up to every customer how he deals with water
consumption. So for ELT this loop is important because it turns the customer behavior in both
cases into an advantage. If a lot of water is consumed a lot of water is generated for flushing and
irrigation, if little is consumed the problem is addressed even better.
Of course in a broader perspective the evapotranspiration losses are recaptured in the bigger fresh
water circle of the planet as rainfall. This water is recollected through the rainwater catchment
system and reused on site. Following this perspective the irrigation of the non edible plants
contribute vastly to the same effect. Here the ecosystem services come into account. When ELT
started the site was a highly degraded ecosystem in a low productive state, with just a few climax
flora species left. The soil was eroded with a minimal to non existing topsoil layer left that could
nearly feed highly adopted pioneer species of predominantly grass varieties. This condition was
mainly created due to overgrazing from goats and abandoned land management. Through fencing
the site, replanting and enriching the soil functions the habitat is now slowly developing into a
productive maquie to forest ecosystem capable of providing water retention, evapotranspiration,
heat reduction etc. This angle allows in our opinion the broader definition of an overall water loop.

Flow Diagram of the existing and new system

The P&Id below (Figure 1.18) shows all water flows within ELT combining the existing system at the lower part of the graphic and the new systems in the upper part. Also, the sensor integration is indicated with the different flow meters and level sensors giving feedback about consumption’s, storage and water flows.

Projected Data of the existing Water demand

The actual demand of water can only be rendered as a simulation where the values are averages of recorded data or assumptions. In reality, it is not accurately predictable how the user will behave in the system and what kind of user will dominate within the whole user group. The design Team of ELT tried to tackle this problem with a consumption range reaching from 80L per person per day (P/d) to 160L P/d incrementally. This defined an upper maximum water consumption and a lower minimum, while ELT created its own consumption pattern based on the different water saving strategies and the tourist in mind. This pattern considered a consumption of 106.6L P/d as realistic value.
Looking at the breakdown by use and water source it is possible to provide around 52% of the total demand by utilizing rainwater.
Within the whole water stream only 9%, consisting of the water for cooking and irrigation, is lost within the first usage cycle (indicated in orange). The remaining 91% is transported to the sewage treatment for reuse (indicated in black/grey).
For ELT this leads to a total water demand of 115.12m within a six month season with a 100% occupation, consisting out of 55.26 fresh water provided by the network and 59.86 from rainwater.

Projected Data of the existing sewage Water production

Through the existing water loop described above also the reclaimed water from the wastewater treatment process contributes to the total water demand. From the overall of 115m water consumed within the lodges, 95.8m finally end up in the treatment facilities; from which 5% is lost due to pipe leaks and around 30% is evapotranspirated in the CW-vf. These assumptions fluctuate throughout time due to degradation of the piping network and weather conditions affecting the water uptake within the wetland. Throughout the season 65% or 68.8m of reclaimed water are available for non-edible plant irrigation or in case of insufficient rainwater for flushing.

Conclusion

In the case of ELT, an average daily consumption of 80L was adopted as the most realistic value. This low consumption would be achieved by combining a mix of factors like very water conscious customers and better overall efficiency of the water saving strategy within ELT. Furthermore, the occupation rate for a new hotel unit is difficult to predict from year to year but reflects heavily on the actual water consumption and respectively to the reclaimed water production. The lack of precise actual data creates an uncertainty and forces the calculations and sizing of the systems generally higher values in order to ensure the safe operation of the system rather than a precise planning according to actual measured values. In the sizing of the new wastewater treatment system IRIDRA and ELT had to assume a value of 80L dark grey water production per PE and day.With the sensor integration this issue will be addressed and more precise data will be generated in the coming years. These long-term data will help following planning processes of NBS for eco- touristic facilities with a focus on low overall water consumption.

Credits:

Text : Nicolas Bedau  and Marilia Kalouli

Illustration : Nicolas Bedau